Executive Summary
This project is being undertaken in response to a request from ODPM Fire Statistics and Research Division (FSRD) to undertake a number of hydraulic calculations on wet and dry risers in high rise buildings. This report provides results of sample calculations using a BRE software package “Riser ﬂow” to calculate water ﬂows in wet and dry risers. The report describes the assumptions made to undertake the calculations and details the results obtained for the speciﬁc conditions requested in the contract proposal, “Fireﬁghting in buildings hydraulic calculation in wet and dry risers, hoses and branches”.

Suitable input data have been identiﬁed. ODPM at a later stage in the project. ODPM under contract CI 71/5/19 to provide an insight into the limitations of ﬁre ﬁghting rising mains complying with BS 5306: Part 1. The project entails the development of PC based calculation software to determine the pressure losses in ﬁre ﬁghting wet and dry rising mains.
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.1 Introduction
This project is being undertaken for Fire Statistics and Research Division (FSRD).1 with speciﬁed ﬁre appliance pumps as the pumping effort. The software will be provided to FSRD. The project includes a series of pressure loss calculations using the software and data provided by the project against speciﬁed scenarios.

8 for an explanation of k factor). pipe diameter (mm). detailed information is required about the system and components. 2. Branch performance characteristics such as nozzle entry pressure (bar) and ﬂow (dm3/min) over the operating pressure range of the branch or the branch k factor (see paragraph 3. Pipe ﬁtting details. 3. such as: 1. The water supply characteristic. hose diameter (mm). Flexible hose details such as length (m). 5. and friction losses through the pipe at ﬂow. (characteristics may vary between different products of the same nominal diameter) and friction losses through the hose under ﬂow conditions (the friction losses may also vary due to pressure). pipe length (m).Background
To predict the pressures and water ﬂows from a branch accurately.
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.1. Pipe size details such as pipe speciﬁcation. change in elevation between inlet and outlet (m). change in elevation between inlet and outlet and end ﬁttings (m). 4.

1.2 Connection details between the pump and the riser
It has been assumed that the connection between the pump and the riser consists of 2 × 70 mm Nominal Diameter (ND) hoses each of 25 m length. Where pumps draw directly from a town main.5 Table 37. speciﬁes the nominal bore size of wet and dry risers.1.
3. depending on the positive pressure at the pump inlet.
3. Clause 7.1 Elements used in the calculations
3.3 Riser inlet connection (breeching)
Each inlet connection complying with BS 5041-33 is required to be ﬁtted with spring loaded non-return valve(s) (see BS 5041-3. but are not readily available within the supplying companies).5 Fitting friction losses for ﬁttings and pipes
The ﬁtting friction losses have been based on BS 5306: Part 2. clause 8. NOTE. Zero suction lift has been assumed for all calculations. No friction loss information has been provided by suppliers of inlet connections.3) and will therefore have a friction loss which exceeds that for straight pipe under ﬂow conditions. See Appendix C.
3. A friction loss equivalent to a single mushroom type non-return valve has therefore been assumed down-stream of the inlet connection. there will be a positive supply pressure advantage. 100 mm ND has been used as this will yield a greater pressure loss than 150 mm ND pipe. Where only one outlet is provided on a ﬂoor a 100 mm ND riser is permitted. A friction loss C factor of 120 has been assumed for BS 1387 Heavy gauge pipe.4 Riser pipe size
BS 5306: Part 1.1.2 unless otherwise stated. (It may be that the friction loss values have been derived during the development of the product. The change in elevation between the pump outlet and riser inlet has been taken as (zero) 0 m. See Appendix B. complying with BS EN 1028-1.1.3 Assumptions and Data used for calculations
3.2.1. Section 18. For all the calculations BS13874 heavy gauge. If two are “permitted” a riser of 150 mm ND is speciﬁed. providing the town main can satisfy the pump demand. galvanised pipe.
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. Calculations of pipework losses have been based on BS 5306: Part 2.1 Water supplies
The pump used for calculation purposes is a Godiva WT30/10 (LP stage).
3.1.

1. 102 k factor 80 230 330
The k factors attributed to the branches are based on performance data made available by the ODPM and data published in Jet/Spray Branches Data sheets. The friction loss equivalent to a “straightway” gate valve has therefore been used. some branches varying more than others. and automaticity.B.1.Assumptions and Data used for calculations
3.
3.
3.
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.8 Branches
The water ﬂow through the branches may be calculated using the equation: –– Q = k√ P Where Q = ﬂow rate through the branch (dm3/min) P = pressure at the entry to the branch (bar) k = nozzle constant The following branches were selected to represent the range of branches available:
SRDB Code No 46 53 45 Details Angloco Ltd – Rosenbauer R. median (SRDB 53) and high (SRDB 45) values within the range of branches for which data are available and also had reasonably consistent k factor values within the 4 to 5 bar operating range. 51 and 70 mm have been included. degree of adjustment.B.6 The available data indicate that the k factors of branches are not always a constant. The branches selected represented those that appeared to represent low (SRBD 46). It is important to note that the k factor values used in this report will not be representative for all possible branch settings or for the full operating branch pressure range of the branch cited. A calculation method and values has been developed for each of the hose sizes that agree closely with one of the UK major hose suppliers’ hydraulic calculation programme. The amount that the k factor varies will be dependent on a number of factors such as bore size.6 Landing valves
No friction loss information has been forthcoming from suppliers for landing valves.1. 201 Walter Frank and Sons – Elkhart chief 4000 -3 Angloco Ltd – Rosenbauer R.7 Hose
Hose diameters of 45.

k = 80
Branch No 46. 51 mm and 70 mm hose connected to the riser outlet.
4. Item 6
The maximum elevation of rising main outlet which if supplied by a BS EN 1028-1 speciﬁcation ﬁre appliance pump is capable to delivering 2 bars pressure at a ﬁreﬁghting branch when supplied through three lengths of British standard BS 6391:1983 45 mm hose connected to the riser outlet. b) two ﬂoors higher than the rising main outlet. k = 230
Branch No 45.5.6 Proposal Appendix A. with the ﬁreﬁghting branch operating a) one ﬂoor higher than the rising main outlet. Assume a notional storey height of 3. k = 80
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. k = 80 60 40 20 0 Hose and Branch selection 70 mm Hose 51 mm Hose 45 mm Hose
Branch No 53. Item 5
The maximum elevation of rising main outlet which if supplied by a BS EN 1028-1 speciﬁcation ﬁre appliance pump is capable to delivering 4 bars pressure at a ﬁreﬁghting branch when supplied through four lengths of British standard BS 6391:1983 45 mm. The details of the assumptions made on which the calculations are based are given in Appendix A. with the branch 3.
Branch No 45. Table A.5 m. The results of the calculations are shown graphically in Figure 9 and the data are provided in numeric form in Appendix A.5 m and 7. k = 330
Branch No 53. k = 330
Branch No 46.5 Proposal Appendix A. Table A. k = 230
Branch No 45. with the ﬁreﬁghting branch operating on the same ﬂoor as the rising main outlet. Maximum branch elevation for a branch pressure of 4 bar 3 × 25 m hose lengths
4.5.0 m above the riser outlet. k = 230
Figure 8. Two sets of calculation were undertaken for four lengths of 25 m hose. k = 330
Branch No 53.Calculation results
160 140 120 Branch elevation – m 100 80 Branch No 46. Both calculation sets were very similar and can be represented by one graph and numeric data set.

51 mm and 70 mm hose connected to the riser outlet. Item 8
The maximum pressures available at a ﬁreﬁghting branch when supplied with three lengths of British standard BS 6391:1983 45 mm. Only one set of data have therefore been plotted. with the ﬁreﬁghting branch operating a) one ﬂoor higher than the rising main outlet.4. The ﬁreﬁghting branch is taken to be operating on the same ﬂoor level as the riser outlet. Table A.4.8.5m. b) two ﬂoors higher than the rising main outlet.
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. The details of the assumptions made on which the calculations are based are given in Appendix A. Table A.7.
180 160 Maximum riser outlet elevation – m 140 120 100 80 60 40 20 0 70 mm ND Hose 51 mm ND hose 45 mm ND Hose Branch 46 Branch 53 Branch 45
Figure 11.8 Proposal Appendix A.7.7 Proposal Appendix A. Table A. 51 mm and 70 mm hose using the performance standard of outlet pressures and pump performance in BS 5306 clause 9. The results of the calculations are shown graphically in Figure 12 and the data are provided in numeric form in Appendix A. Item 7
The maximum elevation of rising main outlet which if supplied by a BS EN 1028-1 speciﬁcation ﬁre appliance pump is capable to delivering 2 bars pressure at a ﬁreﬁghting branch when supplied through four lengths of British standard BS 6391:1983 45 mm. Assume a notional storey height of 3. Maximum riser outlet height for a 2 bar branch pressure
4.Calculation results
4. The results for the branch one and two ﬂoors above the branch outlets were similar values. The results of the calculations are shown graphically in Figure 11 and the data are provided in numeric form in Appendix A.

5. A speciﬁcation for the evaluation of branch performance may be desirable. Caution should be exercised when calculating speciﬁc scenarios to make sure that not only a suitable branch is selected. If a greater hose length is required when connecting at a ﬂoor lower than the point of use. As some branches have throttles controls. below the ﬂoor of use.
5.5 Observations
5. outlet connections and any other ﬁttings where the pressure losses may be signiﬁcant
5. will be more signiﬁcant due to the regulated pressure at the riser outlet. but that the k factor for an appropriate setting is used.2 Riser ﬁttings
Suppliers of riser ﬁttings should be encouraged to provide pressure loss data (based on ﬂow tests) for items such as inlet breechings. this will result in additional pressure losses. To undertake pressure ﬂow calculations on dry risers it has been necessary to attribute speciﬁc pressure/ﬂow characteristics (k factors) to the branches used. providing the total hose length remains constant.4 Choice of branch
The results clearly show that the choice of branch or branch setting is a signiﬁcant variable to achieve satisfactory branch operating pressures. The pressure losses when connecting to a wet riser.3 Branch k factors
The data provided to the project indicates that branch k factors vary considerably.
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.1 Hose connections to riser outlets on ﬂoors beneath the ﬂoor of use
The calculations show the branch pressure differences between connecting a hose to a dry riser outlet on the ﬂoor of use compared to a connection one or two ﬂoors below were not signiﬁcant. Branch suppliers should be encouraged to supply the appropriate branch performance information to carryout such an evaluation accurately. the k factors may vary over the operating range and settings.

Where it is essential to use branches with a high k factor this may require larger hose sizes when working at height or where long lengths of hose are required.6 bar) than the riser pipework is designed and tested to (10 bar).5 Hose
The inﬂuence of hose size on pressure losses decreases with diminishing branch k factor. pipework and ﬁttings
In order to take full advantage of the capability of the pumping appliances. installation and use of rising mains
5.
5.7.
5.3 Riser staging stop valves
Where there is concern that a riser could suffer a catastrophic failure. but this would only be of beneﬁt if higher ﬂow rates were required at relatively low elevations The standard impeller delivered higher pressures at closed system conditions and ﬂowing conditions (14. The HiFlow impeller delivered a maximum of about 10.2 bar and therefore would not exceed current design limitations of the riser pipework.7 Considerations for the design. the rising main. The decline in the HFS-3000 pressure ﬂow curve is more gradual. hoses (inlet).2 Pressure relief of rising mains
Where pumping capacity exceeds the maximum working pressure of the riser consideration should be given to appropriately located pressure relief device or alternatively over pressure alarm device at the inlet to the riser. When a failure occurs the staging valve below the pipe failure and above the riser outlet to be used should be closed.Observations
5.7. consideration should be given to staging stop valves at intervals up the riser.1 Pressure strength of rising main hoses.7.
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. pipework and ﬁttings should be rated to an appropriate potential working pressure.6 bar) and for ﬂows generated by any one branch and hose combination (16. The HFS-3000 standard and HiFlow impeller arrangements yield lower pressures and greater ﬂows than the Godiva WT30/10 pump.
5.6 Pump performance
The Godiva WT30/10 pump is capable of yielding greater pressures (at the pump outlet) at closed system conditions (16.2 bar) than the riser pipework is designed and tested to.
5.

Priming the riser with water would:
G
reduce the ﬁll time and water volume required to bring the riser into use.
5. Consideration should also be given to accessing critical ﬁre alarm. outlet pressures are regulated using pressure reducing valves.8 Riser outlet pressure regulation
Where pressures at risers outlets may exceed operational requirements on wet risers.Hydraulic calculation of wet and dry risers.6 Pressure at wet riser outlets
Current practice limits the wet riser outlet pressure appropriate for hose and branch use on the riser outlet ﬂoor. smoke ventilation and sprinkler installation data.
5.
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The volumes of 63 m high. ﬁre brigade practice should be changed to reﬂect such an installation design change.4 Monitoring of riser stop valves
Any normally open stop valves which may interrupt ﬂow of water through the riser should be electrically monitored and the condition transmitted to a permanently manned location.
5. Water primed risers could be topped up either by a low-ﬂow feed from a header tank at the top of the riser or by an appropriately sized jockey pump at the base. 100 mm ND and 150 mm ND risers would be of the order of 0. In some instances pressure regulating devices may not be correctly adjusted at the time of installation or may become defective with time if not serviced correctly.7 Water priming of dry-risers
Where there is no risk of freezing. Where appropriate. through any riser inlet data relay connection.7. and allow continuous riser condition monitoring. reduce the volume of air to be expelled.7. Pressure reducing valves are most effective when there is a continuous ﬂow.7.5 m3 respectively. Consideration should be given to designing wet risers based on the assumption that the hose connections will be made to the riser below the ﬂoor of use. consideration should be given to permanently priming dryrisers with water at an appropriate standing pressure.7. Loss of water would indicate that integrity of the riser was impaired. Consideration should be given to the use of portable pressure reducing devices
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.
5.7. hoses and branches
5.5 Fire brigade access to riser valve monitoring
Fire brigade access to riser stop valve condition monitoring should preferably be by means of a data relay connection (for a PC with appropriate software) or alternatively by a relay panel at the riser inlet connection.7 m3 and 1. pressures across the regulator may equalise with time if there is no ﬂow.

5.
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. Such devices could be tested and calibrated regularly. At least. based on speciﬁed performance requirements. There are however a number of unknowns such as friction losses through ﬁttings.7.9 Design of wet and dry risers
The requirements of BS 5306:Part 1 are basically sound and pipe sizing practices should limit losses in the risers to comparatively low levels. Consideration should be given to designing wet and dry risers by hydraulic calculation. riser pipework designs should be checked by calculation to establish ﬁtness for purpose.Observations
which may be carried as part of the hose and branch kit.

This group was established to consider the issues. that have been highlighted by the World Trade Centre incident of 11th September 2001.00 ISBN 1 85112 763 1
9 7 8 1 8 5 1 127634
. with speciﬁed ﬁre appliance pumps in speciﬁc scenarios.
ISBN 1-85112-763-1
Price £13.This project was carried out for the Building Disaster Assessment Group in the Ofﬁce of the Deputy Prime Minister. This report provides an insight into the limitations of ﬁre ﬁghting rising mains complying with BS 5306: Part 1. for ﬁre authorities and their ﬁre and rescue services in the UK.